Q1 . The distance is equal to twice the speed of the boat and the speed of the boat is twice the speed of the stream.Find the total time taken to go upstream and downstream?
1. 16/5 hours
2. 16/7 hours
3. 16/3 hours
4. 5 hours
Correct Answer is
16/3 hours
SOLUTION
let the speed of stream be s
then speed of the boat is 2s
so the distance would be 2x2s=4s
total time=4s/(2s-s)+4s/(2s+s)
total time is 16/3 hours
Q2 . The distance travelled by a boat upstream and downstream is 20 km and the total time taken is 5 hours.Find the speed of boat in still water if the speed of the stream is equal to 2 km/h?
1. 12 km/h
2. 20 km/h
3. 22 km/h
4. 2 km/h
Correct Answer is
2 km/h
SOLUTION
the one way distance is 10 km
total time=10/(s+2)+10/(s-2)
total time is 5 hours
substitute and solve the question
we will get a quadratic equation=s^2-4s-4
solving we will get s=2 km/h
Q3 . The distance to be covered is 15 km. The speed of the boat in still water and speed of the stream are3 km/h and 2km/h respectively.Find the time taken to go upstream?
1. 3.5 hours
2. 3 hours
3. 4 hours
4. 2 hours
Correct Answer is
3 hours
SOLUTION
distance/speed=time
15/(3+2)=3 hours
Time taken is 3 hours
Q4 . The total time taken is 10 hours .The speed of the boat in still water and speed of the stream are equal to 25km/h and 15 km/h respectively.Find the total distance covered by the boat?
1. 75 km
2. 85 km
3. 70 km
4. 80 km
Correct Answer is
80 km
SOLUTION
let the distance be d
10=d/(15+25)+d/(25-15)
solving we get the value of d=80 km
Q5 . What should be the speed of the stream such that the total time upstream and douwnstream is 20 hours.The total distance covered is 40 and the speed of the boat in still water is 4 km/h?